As of July 7, nearly 60% of South Dakota is affected by some degree of drought. This week many areas have received moisture, however some of it came with large hail and wind that created additional challenges for producers. This may not be overly significant for some, but it means a change in management decisions for others. Stressors such as drought and hail can increase nitrate levels in forage crops, resulting in a need to change how they are managed.
Stressed Crops as Forage
There are options available for use of stressed crops as forage depending on the severity of the drought or hail. Evaluate the crop to determine which option is the most economical and will give the most opportunities to utilize forage from the crop in the best manner possible. Options, in likely order of use from least to most damaged crops include:
- Test the crop for nitrates to determine if it can safely be used as feed for livestock. SDSU Extension has a Nitrate Quick Test for Forages that will give a positive or negative result for nitrates. If positive, the sample needs to be sent to an analytical laboratory for a quantitative analysis to determine risk. If negative, nitrates are not present and it is safe to feed. Contact SDSU Extension to determine the nearest office providing the test. If there is moderate to no nitrate present, salvaging the crop as livestock forage would be an excellent choice. Depending on the specific level of nitrate present, there are options for blending it with feeds that do not contain nitrates to reach safe levels. Non-pregnant animals can tolerate higher levels of nitrate than pregnant females, so changing the class of cattle that the forage is fed to may be necessary.
- If it won’t make adequate grain and can’t be grazed, harvest the crop for hay. Test for nitrates and have a feed analysis done to determine nutritional value for proper inclusion in a ration. If damage is severe, make sure that it will be worth the diesel, twine and time to make hay.
- Let the crop mature to see if it will produce grain. If they will not produce adequate grain, many crops can be grazed, if necessary precautions are taken (e.g. nitrates) and water and fencing are available.
- Harvest the forage for silage. If nitrates are present, the fermentation process will convert a portion of the nitrate into ammonia, thereby decreasing the overall risk, however it will not completely remove nitrate. It is critical that it is ensiled properly to ensure the best environment for fermentation. A rule of thumb is that 20-50% of the nitrate will be converted to ammonia if the process is done correctly. Always test the ensiled feed before feeding to livestock to ensure that nitrate levels are appropriate for the class of livestock.
- In a worst case scenario where the crop is too damaged or too high in nitrates, consider spraying it out and leaving it for soil cover and reseed directly into it when you get moisture.
Precautions need to be taken when feeding forages that contain nitrates. Details about safety levels and utilizing feeds within different ranges of nitrate content are outlined in Nitrate Poisoning of Livestock: Causes and Prevention. Please see this publication for detailed information.